Unless you for sure are only ever going to run WindowsXP on this machine I'd scoop up another 4 gigs of ram for a total of 8. It's soooooo ridiculously cheap right now to get and Windows 7 64 bit looks like the way to go.

Acer screen? what the hell are you thinking about??? cmon search on the internet a tru 24 inch from LG or samsung at 1920 / 1200 you can find them for like 30 box more. For AMD go with Hyper 212 for cooler, you can mount it any direction you want and it's really cheap can be pricematched for like 24 box I think.
Here are some good screen for a good price;)

Imho get a DDR3 board. When Intel will release their I3 and I5 it will be all DDR3 and AM3 is DDR3 too so DDR2 will go up in price. You can get 4gb of DDR3 1600 at 90$ and the mobo are not much pricier...

Acer is wrong, never think why they are like 100 box under every other brand? they are crap. I have sell to many of them and see to much come back broken to recomend them. At the local shop where I work we just don't sell them anymore because of return %. I think it's horrible.

I've built a number of "Budget" builds for clients & friends and looking at yours it's real nice.

I usually try to get something for nothing in my budget builds so overclocking is the name of the game. Too bad you couldn't get your hands on a unlockable & stable X2 550. Quad for free and overcloks as well.